SV: 1879 Steinway A (jacks)

[A440A@aol.com]

Greetings, 
I wrote: 

>         In regards to the jack's position, I would posit that the most

>important thing is that it be no further under the knuckle than is

required for  dependable actuation.  

Richard writes: 


>>Gotta dissagree. Too far out and the key will miss and you loose power. >>

     Losing power is not dependable actuation!  If it misses, it is too far 
proximal.  There is a point where the jack delivers full power, dependably.  
Any position that is farther distal is wasted friction.  
 
Kjell writes: 
<< 

I think Ed Foote meant the jacks position under the lever (not forwards

or backwards). 20 years ago I learned at the Schimmel factory that the

top of the jack should be positioned just a little bit under the lever

arm (or more correct: the lever arm just a little higher than the top of

the jack, "the thickness of a hair"). Some years later I learned the

same at the Bösendorfer factory. And this weekend Sauter told us the

same at the Nordic Convention in Denmark. << 

    The problem with static dimensions like this is that they do not account 
for wear in the knuckles.  I think the factory advice is somewhat compromised 
to allow the greatest number of techs to get dependable repetition. However, I 
think there is a finer refinement possible;  to wit, (or to half or quarter 
wits, whoever gets involved like me in such obtuse obsession with such abstruse 
concepts.....)
     I set the balancier height so that the jack can be felt to scrape the 
knuckle as it is softly triggered by a finger on the tender, and will return 
under simple spring pressure.  This assures me that there is no lost motion.  
Having the balancier carry as much weight as possible, with the jack still in 
contact, assures the most transparent escapement at ppp levels.  Since I set 
let-off as close to the string excursion zone as possible, this combination(along 
with drop set at the same distance as let-off) gives the greatest sensitivity 
possible without compromising power or repetiton.   I also favor springs that 
cannot be felt in the key when the hammer is released from check.  
Regards, 

 





 





Ed Foote RPT 
http://www.uk-piano.org/edfoote/index.html
www.uk-piano.org/edfoote/well_tempered_piano.html